JP4376826B2 - Co-Cr alloy pellet and method for producing the same - Google Patents

Description

  The present invention relates to a Co—Cr alloy pellet used for casting in the field of dentistry and a method for producing the same.

  Co-Cr alloy (cobalt-chromium alloy) is a material having excellent strength, and is therefore used as a casting material for floors, bars, clasps, maintenance devices and the like in the field of dentistry. Generally, a Co—Cr alloy for dental casting is manufactured by a casting method or the like after melting a metal raw material, and is supplied to the market in the form of a casting pellet of about 5 g to 10 g. In addition, as a prior art of a Co-Cr alloy, the Co-Cr alloy currently disclosed by patent document 1, 2, for example is known.

JP-A-7-48220 JP 2002-206127 A

  A Co—Cr alloy is a material having excellent strength, but it is known that mechanical properties such as ductility are remarkably improved by further adding N (nitrogen). As a method for adding nitrogen to a Co—Cr alloy, a method of blowing nitrogen gas into a molten Co—Cr alloy (bubbling of nitrogen gas), a method of melting a Co—Cr alloy in a high-pressure nitrogen atmosphere A method such as a method of adding a nitride (practically chromium nitride) to a molten Co—Cr alloy is used. However, in the case of bubbling with nitrogen gas, there is a problem that the composition variation of the Co—Cr alloy becomes large. In the case of a method of melting a Co—Cr alloy under a high-pressure nitrogen atmosphere, there is a problem that a production facility for the Co—Cr alloy is large and expensive in order to create a high-pressure nitrogen atmosphere. In the case of a method in which nitride is added when the Co—Cr alloy is melted, since the nitride floats, there is a problem that stable nitriding of the Co—Cr alloy is difficult.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a method for producing Co-Cr alloy pellets for dental casting that is easier and more stable than conventional nitriding. To do.

Means for solving the problems are the following inventions (1) to (7).
(1) A method for producing Co-Cr alloy pellets for dental casting,
A sintering step of obtaining a sintered body having a sintered density of 60% or more and 92% or less by sintering a molded body obtained by molding the raw material powder into a pellet;
And a nitriding step of nitriding the sintered body in an atmosphere containing nitrogen.
(2) A method for producing a Co—Cr alloy pellet according to (1) above,
A method for producing a Co—Cr alloy pellet, wherein a sintering temperature in the sintering step is 900 ° C. or higher and 1350 ° C. or lower.
(3) A method for producing a Co—Cr alloy pellet according to (1) or (2) above,
A method for producing a Co—Cr alloy pellet, wherein the nitriding temperature in the nitriding step is 700 ° C. or higher and 1100 ° C. or lower.
(4) The method for producing a Co—Cr alloy pellet according to any one of (1) to (3) above,
The content of C (carbon) in the raw material powder is {the content of O (oxygen) in the raw material powder × 0.75 + 0.10}% or more; the content of O (oxygen) in the raw material powder × 0.75 + 0.60 } A method for producing Co—Cr alloy pellets, characterized in that it is adjusted to not more than% (% is based on weight).
(5) The method for producing a Co—Cr alloy pellet according to any one of (1) to (4) above,
A method for producing a Co—Cr alloy pellet, characterized in that the content of C (carbon) in the raw material powder is adjusted by adding the carbon powder to the raw material powder.
(6) Co-Cr alloy pellets produced by the method for producing Co-Cr alloy pellets according to any one of (1) to (5) above.
(7) The Co—Cr alloy pellet according to (6) above,
Composition: C: 0.10% to 0.60%, Si: 0.50% to 1.50%, Mn: 0.05% to 0.50%, Ni: 0.20% or less, Cr: 26.00% to 35.00%, Mo: 4.00% to 7.00%, B: 0.10% or less, N: 0.30% to 1.60%, O: 0 Co-Cr alloy pellets characterized by being 20% or less and Fe: 3.00% or less (all are based on weight).

  According to the present invention, Co—Cr alloy pellets for dental casting can be manufactured by a simpler process than using the melt casting method. In addition, stable nitriding of Co—Cr alloy pellets becomes possible.

Hereinafter, embodiments of the present invention will be described in detail.
The present invention relates to a method for producing Co-Cr alloy pellets for dental casting, wherein a sintered body obtained by sintering a raw material powder into a pellet is sintered to have a sintered density of 60% or more and 92% or less. A method for producing a Co—Cr alloy pellet, comprising: a sintering step for obtaining a sintered body; and a nitriding step for nitriding the sintered body in an atmosphere containing nitrogen.
In the present invention, the raw material is not melted and poured into a mold to cast a Co-Cr alloy pellet. To manufacture. In the case of the method for producing Co—Cr alloy pellets according to the present invention, since the casting process is unnecessary, the Co—Cr alloy pellets can be produced with fewer steps compared to the conventional method. In addition, there is no need to melt the raw material, and there is no need for a grinding process such as casting burr of cast pellets, so it is possible to prevent the work environment during production from being deteriorated due to the generation of high heat or the generation of dust. it can.

[Co-Cr alloy pellets]
In the present invention, the composition of the sintered and nitrided Co—Cr alloy pellets is preferably in the range shown in Table 1 below.

  It is preferable that the C (carbon) content is as shown in Table 1. The hardness of the dental Co-Cr alloy is expected to be about Hv 300 to 450, and in order to ensure this hardness This is because the amount of carbon in this range is appropriate. However, in the sintering process, carbon combines with oxygen to form carbon monoxide (see the following formula (II)), so the carbon content after forming and sintering the raw material powder is 0.10%. In order to be 0.60% or less, it is necessary that the raw material powder contains more carbon than this.

  It is preferable that the content of Si (silicon) is as shown in Table 1. The Co—Cr alloy contains a large amount of Cr, so that the oxygen content of the powder tends to be high. If it is high, the amount of carbon after sintering is not stable, so it is necessary to reduce the amount of oxygen in the raw material powder. This is because it is effective to contain 0.5% or more of Si (silicon). On the other hand, if the Si content exceeds 1.5%, the toughness of the Co—Cr alloy decreases, which is not preferable.

It is preferable that the content of Mn (manganese) is as shown in Table 1. The amount of manganese in the raw material powder tends to increase the amount of oxygen, and the raw material powder is spheroidized to form pellets. It is because it reduces. Moreover, since manganese has the effect of improving the toughness of the Co—Cr alloy, it is preferable to contain 0.05% or more.
The reason why the content of Ni (nickel) is preferably as shown in Table 1 is that Ni is considered to be one of the causes of allergies, and therefore it is preferable that the content is smaller. When the Ni content is 0.20% or less, there is almost no influence on the living body.
It is preferable that the content of Cr (chromium) is as shown in Table 1. When the Cr content is less than this range, the corrosion resistance and strength are lowered, and when the Cr content is more than this range, the brittleness is weak. This is because a chemical phase is generated.
It is preferable that the content of Mo (molybdenum) is as shown in Table 1. Mo is necessary for solid solution strengthening and corrosion resistance improvement, and when it is less than 4%, this cannot be fully satisfied. This is because if it exceeds 7%, embrittlement tends to occur.
It is preferable that the content of B (boron) is as shown in Table 1. B is a grain boundary strengthening element and has an effect of improving the strength of the alloy, but if it exceeds this range, the alloy becomes brittle. Because.

  It is preferable that the content of N (nitrogen) is as shown in Table 1. A content of 0.2% or more is sufficient as a material for dental casting, but nitrogen (0. This is because the nitrogen content of the Co—Cr alloy can be stabilized by containing 3% or more. Conversely, if the amount of nitrogen exceeds 1.60%, the amount of nitrogen gas generated increases when the Co—Cr alloy pellets are melted and cast, and the time required for casting becomes longer. However, in the present invention, since the sintered body is nitrided in the nitriding step, it is not always necessary to contain nitrogen in the raw material powder stage.

  It is preferable that the content of O (oxygen) is as shown in Table 1. When the content of O is more than 0.20%, the amount of slag generated when the Co—Cr alloy pellets are melted. This is because there is a risk of increasing the number of casting defects. However, in the present invention, since oxygen can be removed by the reaction of the following formula (II), the oxygen content does not necessarily have to be 0.20% or less at the raw material powder stage.

  The reason why the content of Fe (iron) is preferably as shown in Table 1 is that the corrosion resistance of the Co—Cr alloy decreases when the Fe content exceeds 3.00%.

[Raw material powder]
In this invention, it is preferable to use the raw material powder for manufacturing a Co-Cr alloy pellet whose composition is adjusted according to the composition of the Co-Cr alloy pellet to be obtained.
The raw material powder of the Co—Cr alloy pellet used in the present invention may be prepared by mixing a plurality of types of metal powders, or after melting a plurality of types of metals to produce an alloy, this alloy Metal powder obtained by processing into a powder form may be used.
The particle size of the raw material powder is not particularly limited. The particle size of the raw material powder can be appropriately set according to the moldability of the pellets, the sintered density of the sintered body to be obtained, and the like. The particle size of the raw material powder can be set to be in the range of 10 μm to 500 μm, for example.

As the raw material powder of the Co—Cr alloy pellet used in the present invention, a powder produced by a water spray method or a gas spray method can be used. However, there is a problem that the raw material powder by the gas spray method is expensive, and the obtained powder particles are spherical, so that press molding is slightly difficult. Therefore, the raw material powder obtained by the water spray method is preferable as the raw material powder of the Co—Cr alloy pellet used in the present invention.
Since the raw material powder obtained by the water spray method contains a large amount of oxygen, there is a problem that slag is generated at the time of melting. However, in the present invention, as described later, such a problem can be solved by adding carbon powder to the raw material powder.

[Pellet molding process]
In the method for producing a Co—Cr alloy pellet according to the present invention, the raw material powder prepared as described above is formed into a pellet shape. The shape of the pellet is not particularly limited, and can be formed into, for example, a spherical shape, a cylindrical shape, a rod shape, or a cubic shape. The size of the pellet is not particularly limited, and for example, the pellet can be molded so as to have a size of about 5 g to 10 g.
In order to form the raw material powder into pellets, a known pellet molding machine, press machine, extrusion molding machine or the like can be used. In addition, when shape | molding raw material powder to a pellet form, it is preferable to add the lubricant etc. for reducing the friction with a molding machine with respect to raw material powder. In addition, when the raw material powder is formed into a pellet, it is one means to add a resin binder or the like in order to improve the moldability and shape retention of the pellet. Since the lubricant and the resin binder contaminate the sintering furnace, it is preferable to perform a degreasing step for removing them before the sintering step.

[Sintering process]
In the present invention, a sintered body having a sintered density of 60% or more and 92% or less is manufactured by sintering a formed body obtained by forming the raw material powder into a pellet. The “sintered density” here is an index of “denseness” of the sintered body, and can be calculated by, for example, the following equation (I).
(Bulk density of sintered body [g / cm ³ ]) / (true density of alloy of sintered body composition [g / cm ³ ]) × 100 (%) (I)

  In the above formula (I), the bulk density of the sintered body is a density obtained using the volume calculated using the outer dimensions of the sintered body, for example (the voids inside the sintered body are also The density is assumed to be a part of the sintered body). The true density of metal is the theoretical density when voids are not included inside. That is, a high sintered density means that there are few voids inside the sintered body and the sintered body is more densely formed.

In the present invention, the sintered density of the sintered body (Co—Cr alloy pellets) is set in the range of 60% to 92% based on the following reasons.
When the sintered density of the Co—Cr alloy pellet is smaller than 60%, the high frequency input efficiency when the Co—Cr alloy pellet is melted is lowered. In this case, there is a problem that the Co—Cr alloy pellets are not sufficiently melted and defects such as voids may be generated inside the cast product.
On the other hand, when the sintered density of the Co—Cr alloy pellet is larger than 92%, many fine closed pores exist inside the pellet. In this case, when the pellets are melted, the gas confined in these closed pores cannot be sufficiently removed, and defects such as voids may occur in the cast product. In addition, when the Co—Cr alloy pellets are melted and heated, excess nitrogen components contained in the Co—Cr alloy pellets are released as nitrogen gas, but when the sintered density is greater than 92% , The release of nitrogen gas before melting is insufficient (because there are few pores leading to the surface of the pellet), and this nitrogen gas causes bubbling during melting or defects in the cast There is a problem.
In addition, when the sintered density of the Co—Cr alloy pellet is larger than 92%, the pores leading to the surface of the pellet are reduced. Nitridation cannot be performed (this will be described in detail in [Nitriding step]).

By the way, since a Co—Cr alloy contains a large amount of chromium as its composition, the powder contains O (oxygen). Further, as described above, when a raw material powder obtained by water spray is used, the raw material powder contains a large amount of O (oxygen). Such oxygen is preferably removed as much as possible because it causes slag generation when the Co—Cr alloy pellets are dissolved. In the present invention, oxygen contained in the Co—Cr alloy can be removed by causing a reaction of the following formula (II) in the sintering step.
C (carbon) + O (oxygen) → CO gas ↑ ... (II)

In order to remove the oxygen by causing the reaction of the above formula (II) and adjust the carbon content of the Co—Cr alloy pellets to the range shown in Table 1, the content of C (carbon) in the raw material powder is: It is preferably adjusted within a range represented by the following formula (III).
{O (oxygen) content of raw material powder x 0.75 + 0.10}% or more,
{O (oxygen) content of raw material powder x 0.75 + 0.60}% or less (% is based on weight) (III)

In the above formula (III), the number “0.75” is the value of the ratio of the atomic weight of C and O. By adjusting the C (carbon) content of the raw material powder (Co—Cr alloy) to the range of the above formula (III), O (oxygen) contained in the raw material powder is almost removed. Even when carbon in the raw material powder is consumed to remove oxygen, the content of C (carbon) in the sintered and nitrided Co—Cr alloy pellets is 0.10% or more and 0 It is maintained in the range of 60% or less.
In order to adjust the C (carbon) content of the raw material powder to the range of the above formula (III), carbon may be added to the raw material powder. The carbon is preferably added in the form of carbon powder such as carbon black, but may be added in the form of other compounds or carbides containing C (carbon). By adding carbon in the form of carbon powder to the raw material powder, the content of C (carbon) in the raw material powder can be adjusted more easily and accurately.

In order to remove oxygen in the raw material powder to 0.20% or less, the sintering temperature in the sintering step is preferably 900 ° C. or higher and 1350 ° C. or lower, and preferably 1050 ° C. or higher and 1350 ° C. or lower. Is more preferable. This is because the reaction of the above formula (II) can be caused to proceed more reliably by heating and sintering the molded body at a temperature within this range. Moreover, it is because the required intensity | strength as a sintered compact can be ensured more reliably by sintering with the heating temperature of this range. The sintering atmosphere may be an atmosphere in which the reaction is stable. Practically, vacuum pressure, Ar (argon), N ₂ fine pressure (5-20 Torr), ammonia (decomposition gas), etc. can be used. .

[Nitriding process]
In the method for producing a Co—Cr alloy pellet according to the present invention, a sintered body is produced by sintering a molded body obtained by forming raw material powder into a pellet shape, and this sintered body is subjected to an atmosphere containing nitrogen. Nitrid under. In order to nitride the sintered body, nitrogen gas may be introduced into the atmosphere during the cooling process of the sintered body, or it may be nitrided by heating again after cooling the sintered body. In the case of sintering in an ammonia atmosphere, it is possible to simultaneously perform nitriding in the process of cooling the sintered body.
By nitriding the sintered body, the sintered body contains nitrogen in the form of chromium nitride or the like. Since this chromium nitride decomposes at 1250 ° C. or higher, the nitriding temperature needs to be 1250 ° C. or lower. On the other hand, when the nitriding temperature is too low, the nitriding rate is slowed down, so that the time required for nitriding becomes long. Therefore, the nitriding temperature in the nitriding step is preferably 700 ° C. or higher and 1100 ° C. or lower. When the nitriding temperature is within this range, the sintered body can be nitrided quickly and stably.

In the method for producing a Co—Cr alloy pellet according to the present invention, the sintered density of the sintered body is set to 60% or more and 92% or less, and pores communicating with the surface of the sintered body are formed inside the sintered body. Many voids are formed. Therefore, by nitriding the sintered body in an atmosphere containing nitrogen, it is possible to nitride not only the surface portion of the sintered body but also the inside of the sintered body.
Further, in the case of the method according to the present invention, it is only necessary to nitride the sintered body. Therefore, unlike the conventional method, it is not necessary to melt the raw material powder and blow in nitrogen gas. In this case, since it is not necessary to create high heat for melting the raw material powder, the working environment when manufacturing the Co—Cr alloy pellets is improved.

  In addition, in the case of the method according to the present invention, unlike the production of Co—Cr alloy pellets by the melt casting method, the raw material powder is simply formed into pellets and sintered. Therefore, a process of removing cast burrs and the like of the cast product pellets by grinding is unnecessary, and it is possible to prevent the working environment from being deteriorated by dust made of grinding powder.

  According to the method for producing a Co—Cr alloy according to the present invention, a sufficient amount of nitrogen can be contained in a Co—Cr alloy pellet, and the mechanical properties of a cast product made of a Co—Cr alloy, in particular, Ductility can be significantly improved. For example, the mechanical properties of dental parts such as floors, bars, clasps and maintenance devices can be significantly improved.

Hereinafter, more specific examples of the present invention will be described.
First, raw material powder of a Co—Cr alloy obtained by a water spray method was prepared. This raw material powder has a particle size adjusted by passing through a 100-mesh sieve, and its composition is as shown in Table 2 below.
The content of O (oxygen) in the raw material powder is 0.70%. Therefore, it is theoretically necessary to add 0.70 × 0.75 = 0.525% of carbon in order to cause the reaction of the above formula (II) to remove oxygen. Moreover, in order to maintain the carbon content of the sintered body in the range of 0.10% or more and 0.60% or less, the carbon content of the raw material powder is reduced by adding carbon to the raw material powder. It is necessary to adjust so that it may become 0.625% or more and 1.125% or less.

  After adding carbon powder and a non-metal-containing lubricant to the prepared raw material powder, the raw material powder was formed into a cylindrical shape having a diameter of 16 mm and a height of 5 mm by a press. The addition amount of the lubricant was 1% with respect to the whole raw material powder. The press molding pressure was 500 MPa. The obtained molded body was degreased for 1 hour at a temperature of 500 ° C. in a nitrogen gas atmosphere, and then the molded body was heated at a temperature of 1180 ° C. for 1 hour to be sintered. The sintering atmosphere was performed with vacuum and ammonia gas, respectively. The composition of the sintered body thus obtained was analyzed. The analysis results are shown in Table 3 below.

  As can be seen from the results shown in Table 3, it was found that the oxygen content of the sintered body can be reduced to 0.2% or less by adding carbon to the raw material powder. It was also found that the sintered body can contain 0.30% or more of nitrogen by cooling the formed body made of the raw material powder in an ammonia gas atmosphere and then cooling it as it is. It has also been found that the amount of carbon contained in the sintered body can be controlled by adjusting the amount of carbon in the raw material powder.

  Next, the sintered body obtained in Example 1 (NO.3 sintered body in Table 3) was heated in an atmosphere containing nitrogen to perform nitriding treatment. The results are shown in Table 4 below.

  It has been found that the sintered body can be easily nitrided by heating in an atmosphere containing nitrogen. Further, as can be seen from the results shown in Table 4, it has been found that the nitrogen content is not sufficient when the nitriding temperature is lower than 700 ° C., and the nitrogen content is hardly increased when the nitriding temperature is higher than 1100 ° C. From this, it was found that the nitriding temperature in the nitriding step is preferably 700 ° C. or higher and 1100 ° C. or lower.

  Further, as can be seen from the results shown in Table 4, the nitrogen content of the cast product after melting and casting the nitridated Co—Cr alloy pellets is such that the nitrogen content of the Co—Cr alloy pellets is 0.40% or more. In this case, it was found to be constant at about 0.30%. This is considered to be caused by the fact that excess nitrogen is released during the heating and melting of the Co—Cr alloy pellets and that the melting temperature of the Co—Cr alloy becomes substantially constant depending on the solubility of nitrogen.

  Next, the NO. 1-NO. The sintered body obtained in 6 was subjected to nitriding treatment by heating at 900 ° C. for 1 hour in an atmosphere containing nitrogen. After the nitriding-treated Co—Cr alloy pellets were melted at high frequency, a tensile test piece having a parallel part of 3 mm in diameter and 15 mm in length and a small plate for hardness measurement were produced by a pressure casting machine. And the tension test and the hardness test were done using the obtained tensile test piece and the small plate. The tensile test method was in accordance with JIS-Z-2241. These results are shown as NO. 17-NO. 22 shows.

  Moreover, as a comparative example, a cast product obtained by adding a nitride at the time of melting of a casting product pellet (M1, M2) obtained by melting a Co—Cr alloy material and a Co—Cr alloy material. The pellets (MN1, MN2) were similarly tested. The test results are shown in Table 6 below.

  As can be seen from the comparison of the results in Table 5 and Table 6, the cast product (Table 5) obtained by melting the Co-Cr alloy pellet obtained by nitriding the sintered body melts the cast product pellet. It was found that nitrogen was contained more stably than the obtained cast product (Table 6), and physical strength, particularly elongation (ductility) was excellent.

  In Example 4, first, a Co—Cr alloy raw material powder obtained by a water spray method was prepared. This raw material powder has a particle size adjusted by passing through a 100 mesh sieve, and its composition is as shown in Table 2 above. To this raw material powder, a fine powdery raw material powder having the composition shown in Table 7 below and having a particle size of 30 μm or less and an average particle size of 8.5 μm was mixed. Furthermore, with respect to the powder after mixing, carbon powder (carbon powder whose amount is adjusted so that the amount of residual carbon after the reaction of the above formula (II) occurs is 0.15%) and a lubricant. Was added to form a cylindrical body having a diameter of 16 mm and a height of 5 mm at a pressure of 100 MPa to 600 MPa. This molded body was sintered at a heating temperature of 1250 ° C. for 1 hour in a vacuum state to obtain a sintered body. Thereby, a plurality of types of sintered bodies having different sintered densities were obtained. Nitrogen was introduced during the cooling process (900 ° C.) of these sintered bodies and nitrided for 1 hour. Thereby, a plurality of types of sintered bodies (Co—Cr alloy pellets) having different sintering densities and C, O, and N contents were obtained (P1 to P8). The sintered density of the sintered body and the results of the composition analysis of the sintered body are shown in Table 8 below.

P1-P8 sintered bodies (Co—Cr alloy pellets) were melted at a high frequency, and a tensile test piece and a hardness measurement plate were cast by a pressure casting machine in the same manner as in Example 3. Table 8 shows the result of composition analysis of the obtained casting. Findings during melting of Co-Cr alloy pellets (results of visual observation), time until the Co-Cr alloy pellets melt, results of tensile test of cast product, results of hardness test of cast product, and cast product Table 9 shows the findings of the microstructure when observed with a microscope.

  From the results shown in Table 9, when the sintered density is less than 60%, it takes time to melt the Co—Cr alloy pellets, the unmelted sintered body floats on the metal after melting, and remains undissolved. It was found that there was a phenomenon. Further, it has been found that when the sintered density exceeds 92%, the flotation of pores and inclusions is restricted, and defects such as voids (voids) and inclusions (residues such as lumps) of the cast product are likely to occur.

  Further, from the results shown in Table 9, it was found that the sintered density of the sintered body is increased by mixing the raw powder with fine powder having a particle size of 30 μm or less. However, in this case, since pores and inclusions existing in the sintered body are difficult to float and remain in the cast product, it has been found that defects such as inclusions and voids are likely to occur in the microstructure of the cast product. Further, it was found that if the sintered density of the sintered body is too high, nitriding is not sufficient, so that the nitrogen content of the Co—Cr alloy pellets is lowered. From the above, it was found that the sintered density of the sintered body is preferably 60% or more and 92% or less in order to increase the physical strength (particularly elongation) of the cast product.

Claims (7)

A method for producing Co-Cr alloy pellets for dental casting,
A sintering step of obtaining a sintered body having a sintered density of 60% or more and 92% or less by sintering a molded body obtained by molding the raw material powder into a pellet;
And a nitriding step of nitriding the sintered body in an atmosphere containing nitrogen. It is a manufacturing method of the Co-Cr alloy pellet according to claim 1,
A method for producing a Co—Cr alloy pellet, wherein a sintering temperature in the sintering step is 900 ° C. or higher and 1350 ° C. or lower. It is a manufacturing method of the Co-Cr alloy pellet according to claim 1 or 2,
A method for producing a Co—Cr alloy pellet, wherein the nitriding temperature in the nitriding step is 700 ° C. or higher and 1100 ° C. or lower. It is a manufacturing method of the Co-Cr alloy pellet according to any one of claims 1 to 3,
The content of C (carbon) in the raw material powder is {the content of O (oxygen) in the raw material powder × 0.75 + 0.10}% or more; the content of O (oxygen) in the raw material powder × 0.75 + 0.60 } A method for producing Co—Cr alloy pellets, characterized in that it is adjusted to not more than% (% is based on weight). A method for producing a Co-Cr alloy pellet according to any one of claims 1 to 4,
A method for producing a Co—Cr alloy pellet, characterized in that the content of C (carbon) in the raw material powder is adjusted by adding the carbon powder to the raw material powder.   The Co-Cr alloy pellet manufactured by the manufacturing method of the Co-Cr alloy pellet of any one of Claims 1-5. The Co-Cr alloy pellet according to claim 6,
Composition: C: 0.10% to 0.60%, Si: 0.50% to 1.50%, Mn: 0.05% to 0.50%, Ni: 0.20% or less, Cr: 26.00% to 35.00%, Mo: 4.00% to 7.00%, B: 0.10% or less, N: 0.30% to 1.60%, O: 0 Co-Cr alloy pellets characterized by being 20% or less and Fe: 3.00% or less (all are based on weight).